Immune stress markedly affects the immune function and growth performance of livestock, including poultry, resulting in financial loss to farmers. It can lead to decreased feed intake, reduced growth, and intestinal disorders. Studies have shown that pathogen-induced immune stress is mostly related to TLR4-related inflammatory signal pathway activation, excessive inflammatory cytokine release, oxidative stress, hormonal disorders, cell apoptosis, and intestinal microbial disorders. This paper reviews the occurrence of immune stress in livestock, its impact on immune function and growth performance, and strategies for immune stress prevention.

Introduction: The widespread use of antibiotics in animal agriculture has increased the resistance of Escherichia coli, and pathogenic E. coli often harbor complex virulence factors. Antimicrobial resistance in pathogenic bacteria can cause public health problems. Correlation analyses of the resistance, virulence, and serotype data from the pathogenic bacteria found on farms and in the surrounding environment can thus provide extremely valuable data to help improve public health management.Methods: In this investigation, we have assessed the drug resistance and virulence genes as well as the molecular typing characteristics of 30 E. coli strains isolated from duck farms in the Zhanjiang area of China. Polymerase chain reaction was used to detect the drug resistance and virulence genes as well as serotypes, and whole-genome sequencing was used to analyze the multilocus sequence typing.Results: The detection rates for the oqxA resistance gene and fimC virulence gene were highest (93.3%, respectively). There were no correlations between the drug resistance and virulence gene numbers in the same strain. The epidemic serotype was O81 (5/24), ST3856 was an epidemic sequence type, and strains I-9 and III-6 carried 11 virulence genes. The E. coli strains from the duck farms in the Zhanjiang area were thus found to have a broad drug resistance spectrum, various virulence genes, complex serotypes, and certain pathogenicity and genetic relationship.Discussion: Monitoring the spread of pathogenic bacteria and the provision of guidance regarding the use of antibiotics in the livestock and poultry industries will be required in the future in the Zhanjiang area.

Introduction: The antibacterial protein PAG14 was extracted from a metabolite of Bacillus G14 isolated from mangrove plants.Methods: In this study, Pseudomonas aeruginosa, Pasteurell multocide, Enterobacter aerogenes, and Enterococcus faecalis were used as indicator bacteria to screen endophytes that exhibited antibacterial activity. The endophyte culture conditions were optimized to enhance productivity. Subsequently, the culture supernatant was salted using ammonium sulfate, followed by purification using dextran gel chromatography and ion exchange column techniques. Finally, the structures of antibacterial proteins were identified using mass spectrometry.Results and Discussion: The optimal culture conditions for Bacillus G14 were 2% mannitol, 0.5% fish peptone, 0.05% KH2PO4 + 0.05% K2HPO4 + 0.025% MnSO4·H2O. The antibacterial substances exhibited stability within the temperature range of 30–40°C and pH range of 5.0–7.0, while displaying sensitivity toward enzymes. The antibacterial activity decreased as the duration of UV irradiation increased. The antibacterial protein PAG14, isolated from the culture broth of Bacillus G14 through purification using dextran gel and ion-exchange columns, was identified as a class III bacteriocin using LC-MS/MS, similar to Lysozyme C. These findings serve as a theoretical foundation for the investigation and application of bacteriocins in food products.

Listeria monocytogenes is a significant zoonotic pathogen capable of forming biofilms on food and other materials, representing a considerable risk to human health and animal husbandry. The use of bacteriocins as potential new antibacterial and antibiofilm reagents has attracted considerable interest. This study aimed to determine the inhibitory effects of bacteriocin PCM7−4 on L. monocytogenes biofilm formation. In this study, bacteriocin PCM7−4 of SICs (1/16 × MIC, 1/8 × MIC) significantly inhibited the formation of L. monocytogenes biofilm. Bacteriocin PCM7−4 of SICs significantly reduced the production of bacterial extracellular polysaccharides, and could decrease the bacterial motility, meanwhile, PCM7−4 significantly reduced the number and viability of bacteria within the biofilm. RT-qPCR results showed that bacteriocin PCM7−4 significantly reduced the expression of flagella, community sensing and virulence factor genes associated with biofilm formation. The results demonstrated the considerable potential of bacteriocin PCM7−4 as a therapeutic agent for the prevention and treatment of L. monocytogenes biofilms.

Guangdong Province is an important area of poultry breeding in China. Zhanjiang city is located in the western part of Guangdong Province, where there are many broiler farms. To investigate antimicrobial resistance (AMR) and the presence of resistance genes in Escherichia coli from broiler farms, a total of 220 samples were collected from soil and feces at eight broiler farms. Subsequently, 220 strains of E. coli were isolated for drug resistance analysis and detection of AMR genes. The results revealed that the isolated E. coli strains exhibited high prevalence of multidrug resistance to 12 antimicrobial drugs including amoxicillin, tetracycline, cotrimoxazole and sulfisoxazole. Among the isolated strains, 95% of the isolates were resistant to more than three antimicrobial agents; notably, thirty-nine strains showed multidrug resistance to ten tested drugs, while four strain exhibits multidrug resistance to as many as fifteen antibacterial drugs. Additionally, seven AMR genes such as bla _TEM and sul2 were detected in over half (≥50%) of the isolated E. coli samples; thirteen AMR genes had relatively low detection prevalence (≤30%). Correlation analysis indicated a strong association between certain AMR genes ( bla _TEM , pexA, aadA1, bla _AIM , ant(3")-I, sul2, sul3, tet(D) ) and AMR (≥50%). In conclusion, E.coli strains obtained from soil and fecal samples in broiler farms exhibited multidrug resistant phenotypes along with carrying various AMR genes. This provides a reference for the scientific control of E. coli multidrug resistance in this area.